netdev - [Patch net 06/12] codel: remove sch->q.qlen check before qdisc_tree_reduce

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Message-Id: <20250320232539.486091-6-xiyou.wangcong@gmail.com>
Date: Thu, 20 Mar 2025 16:25:33 -0700
From: Cong Wang <xiyou.wangcong@...il.com>
To: netdev@...r.kernel.org
Cc: jhs@...atatu.com,
	jiri@...nulli.us,
	edumazet@...gle.com,
	gerrard.tai@...rlabs.sg,
	Cong Wang <xiyou.wangcong@...il.com>
Subject: [Patch net 06/12] codel: remove sch->q.qlen check before qdisc_tree_reduce_backlog()

After making all ->qlen_notify() callbacks idempotent, now it is safe to
remove the check of qlen!=0 from both fq_codel_dequeue() and
codel_qdisc_dequeue().

Reported-by: Gerrard Tai <gerrard.tai@...rlabs.sg>
Signed-off-by: Cong Wang <xiyou.wangcong@...il.com>
---
 net/sched/sch_codel.c    | 5 +----
 net/sched/sch_fq_codel.c | 6 ++----
 2 files changed, 3 insertions(+), 8 deletions(-)

diff --git a/net/sched/sch_codel.c b/net/sched/sch_codel.c
index 81189d02fee7..12dd71139da3 100644
--- a/net/sched/sch_codel.c
+++ b/net/sched/sch_codel.c
@@ -65,10 +65,7 @@ static struct sk_buff *codel_qdisc_dequeue(struct Qdisc *sch)
 			    &q->stats, qdisc_pkt_len, codel_get_enqueue_time,
 			    drop_func, dequeue_func);
 
-	/* We cant call qdisc_tree_reduce_backlog() if our qlen is 0,
-	 * or HTB crashes. Defer it for next round.
-	 */
-	if (q->stats.drop_count && sch->q.qlen) {
+	if (q->stats.drop_count) {
 		qdisc_tree_reduce_backlog(sch, q->stats.drop_count, q->stats.drop_len);
 		q->stats.drop_count = 0;
 		q->stats.drop_len = 0;
diff --git a/net/sched/sch_fq_codel.c b/net/sched/sch_fq_codel.c
index 799f5397ad4c..6c9029f71e88 100644
--- a/net/sched/sch_fq_codel.c
+++ b/net/sched/sch_fq_codel.c
@@ -315,10 +315,8 @@ static struct sk_buff *fq_codel_dequeue(struct Qdisc *sch)
 	}
 	qdisc_bstats_update(sch, skb);
 	flow->deficit -= qdisc_pkt_len(skb);
-	/* We cant call qdisc_tree_reduce_backlog() if our qlen is 0,
-	 * or HTB crashes. Defer it for next round.
-	 */
-	if (q->cstats.drop_count && sch->q.qlen) {
+
+	if (q->cstats.drop_count) {
 		qdisc_tree_reduce_backlog(sch, q->cstats.drop_count,
 					  q->cstats.drop_len);
 		q->cstats.drop_count = 0;
-- 
2.34.1